TCP in C (one server and multiple clients)

     
    #include"stdio.h"
    #include"stdlib.h"
    #include"sys/types.h"
    #include"sys/socket.h"
    #include"string.h"
    #include"netinet/in.h"

    #define PORT 4444
    #define BUF_SIZE 2000
    #define CLADDR_LEN 100

    void main() {
     struct sockaddr_in addr, cl_addr;
     int sockfd, len, ret, newsockfd;
     char buffer[BUF_SIZE];
     pid_t childpid;
     char clientAddr[CLADDR_LEN];
     
     sockfd = socket(AF_INET, SOCK_STREAM, 0);
     if (sockfd < 0) {
      printf("Error creating socket!\n");
      exit(1);
     }
     printf("Socket created...\n");
     
     memset(&addr, 0, sizeof(addr));
     addr.sin_family = AF_INET;
     addr.sin_addr.s_addr = INADDR_ANY;
     addr.sin_port = PORT;
     
     ret = bind(sockfd, (struct sockaddr *) &addr, sizeof(addr));
     if (ret < 0) {
      printf("Error binding!\n");
      exit(1);
     }
     printf("Binding done...\n");

     printf("Waiting for a connection...\n");
     listen(sockfd, 5);

     for (;;) { //infinite loop
      len = sizeof(cl_addr);
      newsockfd = accept(sockfd, (struct sockaddr *) &cl_addr, &len);
      if (newsockfd < 0) {
       printf("Error accepting connection!\n");
       exit(1);
      }
      printf("Connection accepted...\n");

      inet_ntop(AF_INET, &(cl_addr.sin_addr), clientAddr, CLADDR_LEN);
      if ((childpid = fork()) == 0) { //creating a child process

       close(sockfd); 
    //stop listening for new connections by the main process. 
    //the child will continue to listen. 
    //the main process now handles the connected client.

       for (;;) {
        memset(buffer, 0, BUF_SIZE);
        ret = recvfrom(newsockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &cl_addr, &len);
        if(ret < 0) {
         printf("Error receiving data!\n");  
         exit(1);
        }
        printf("Received data from %s: %s\n", clientAddr, buffer); 

        ret = sendto(newsockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &cl_addr, len);   
        if (ret < 0) {  
         printf("Error sending data!\n");  
         exit(1);  
        }  
        printf("Sent data to %s: %s\n", clientAddr, buffer);
       }
      }
      close(newsockfd);
     }
    }

     
    #include"stdio.h"  
    #include"stdlib.h"  
    #include"sys/types.h"  
    #include"sys/socket.h"  
    #include"string.h"  
    #include"netinet/in.h"  
    #include"netdb.h"
      
    #define PORT 4444 
    #define BUF_SIZE 2000 
      
    int main(int argc, char**argv) {  
     struct sockaddr_in addr, cl_addr;  
     int sockfd, ret;  
     char buffer[BUF_SIZE];  
     struct hostent * server;
     char * serverAddr;

     if (argc < 2) {
      printf("usage: client < ip address >\n");
      exit(1);  
     }

     serverAddr = argv[1]; 
     
     sockfd = socket(AF_INET, SOCK_STREAM, 0);  
     if (sockfd < 0) {  
      printf("Error creating socket!\n");  
      exit(1);  
     }  
     printf("Socket created...\n");   

     memset(&addr, 0, sizeof(addr));  
     addr.sin_family = AF_INET;  
     addr.sin_addr.s_addr = inet_addr(serverAddr);
     addr.sin_port = PORT;     

     ret = connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));  
     if (ret < 0) {  
      printf("Error connecting to the server!\n");  
      exit(1);  
     }  
     printf("Connected to the server...\n");  

     memset(buffer, 0, BUF_SIZE);
     printf("Enter your message(s): ");

     while (fgets(buffer, BUF_SIZE, stdin) != NULL) {
      ret = sendto(sockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &addr, sizeof(addr));  
      if (ret < 0) {  
       printf("Error sending data!\n\t-%s", buffer);  
      }
      ret = recvfrom(sockfd, buffer, BUF_SIZE, 0, NULL, NULL);  
      if (ret < 0) {  
       printf("Error receiving data!\n");    
      } else {
       printf("Received: ");
       fputs(buffer, stdout);
       printf("\n");
      }  
     }
     
     return 0;    
    }